Linear and non-linear viscoelastic behaviors of crosslinked tapioca starch/polysaccharide systems

Abstract

Effects of polysaccharides on both the thickening performance and large deformation behavior of mixtures of various crosslinked tapioca starch and polysaccharide were investigated. It was found that the gelatinized crosslinked tapioca starch at 1–8%w/w in aqueous solutions behaved as swollen granules with the low-shear viscosity described by Krieger & Dougherty equation. To achieve thickening performance, 3.5%w/w starch was cooked with a range of 0.5%w/w polysaccharides, i.e. konjac glucomannan, guar gum, xanthan gum, and their 50:50 mixtures. It was shown that additions of polysaccharides greatly affected the rheological behavior of the suspensions, predominantly in the linear viscoelastic regime. The studied mixtures of starch and polysaccharides exhibited strong synergistic effects as evidenced from the increase in their consistency coefficients and the excess storage moduli calculated from the Palierne equation. Moreover, the mixtures containing xanthan gum showed weak-gel characteristics while the others demonstrated liquid-like behavior. In the non-linear viscoelastic analysis, arrangement of starch granules and specific interfacial interactions evidently affected the deformation behavior of the mixtures of crosslinked tapioca starch and polysaccharide. The mixture of konjac glucomannan and xanthan also largely improved stress susceptibility of the suspension and gave the unique shear stiffening under large amplitude oscillatory shear experiment.